1. Field of the Invention
This invention relates to in-line roller skate wheels and more particularly to a pre-pressurized pneumatic skate wheel of integral polyurethane construction having contour conforming tire support wall.
2. Description of the Prior Art
Roller skates and roller skate wheels have been known in the art. Typically, roller skates have incorporated four wheels in each skate. Early wheels were constructed of either wood or metal depending on the intended use. Wood wheels were most often used for indoor roller rink skating while metal wheels were used for outdoor skating. Inflatable roller skate wheels, such as that disclosed in U.S. Pat. No. 988,533 to Zverina, provided a simple, durable and economic roller skate wheel. Zverina includes an inflatable tube encased in a conventional tire.
In the past, many skate wheels were constructed of rubber. The availability of polyurethane in skate wheel construction has enhanced the enjoyment and popularity of outdoor skating. Typically roller skates have been constructed with four wheels in a box-like configuration. Such skates, while functional, do not allow for the freedom of movement experienced by ice skaters. It was thus proposed to mount the roller skate wheels in a line along the skate frame to achieve mobility which closely mimicked the movement of an ice skate. Since that time, "in-line roller skates" have become one of the most popular recreational and physical fitness activities in the United States, and elsewhere. In-line skating has also developed into a highly sophisticated and technologically advancing commercial market.
The recreational skater often travels a variety of terrains ranging from concrete and wood to more bumpy and uneven surfaces such as asphalt which may exhibit bumps, pits and even wide cracks with vegetation growing therein. The main concern experienced by the recreational skater is to obtain a comfortable ride while skating socially, participating in physical fitness or even just a way to reach a destination. This skater requires a resilient wheel which is light weight and shock resistant. More experienced skaters, such as competitive skaters, employ in-line skates for sporting purposes such as hockey or road racing. Dancers typically prefer relatively hard tire bodies since some slippage is an acceptable compromise for the performance required. On the other hand, a hockey player would prefer a softer tire having excellent surface gripping characteristics. In the past, these various performance characteristics have been attained only by expensive painstaking manufacturing processes.
Polyurethane in-line skate wheels proposed in the past have typically been constructed by injection molding to form a hub surrounded by a tire body of solid urethane. It is desirable that such wheels provide a durable and relatively smooth ride over many types of terrains. Solid polyurethane bodies have been proposed. Such tire bodies are necessarily restricted in that the performance characteristics cannot be easily and inexpensively adjusted during the manufacturing process to accommodate the many different support surfaces and loads emanated by a skate employed in a demanding sport such as, for instance, hockey. Unlike a traditional quad or box-style roller skate, in-line skates are designed to withstand a variety of different side loads due to the inclination of the skate along its horizontal axis when turning, as well as high intensity shock loads from quick stops, bumps and other road hazards. Thus the designers of in-line skate wheels have an intensely difficult task when faced with such diverse performance requirements. One attempt to solve the shock absorption and performance problems can be found in the injection molded tire shown in U.S. Pat. No. 5,312,844 to Goniser. Goniser discloses a wheel incorporating a hard urethane hub and a softer, injection molded solid body polyether type polyurethane tire formed on the hub. Wheels of this type have not gained general acceptance in the in-line U.S. skate market. It is believed that the tire bodies in such wheels cannot be easily and inexpensively made to exhibit the characteristics demanded by users. The capital cost for each injection mold is considerable thus limiting the number of styles of tires that can be manufactured cost effectively with different operating characteristics.
Thus, there exists a need for a skate wheel which can be inexpensively casted from thermoset polyurethane by a method which allows for convenience adjustment of the tire body to exhibit different operating characteristics without the necessity of making entirely new molds or involving an expensive development procedure to develop new or different thermoplastic urethane. It has been discovered that soft polyurethane exhibits desirable characteristics for in-line skate wheels in that the outer peripheral tread surface tends to flex and compress in response to forces associated with rolling contact under load involving irregular support surfaces. However, solid thermoplastic polyurethane tire bodies suffer the shortcoming that they consume a substantial quantity of polyurethane and that the force absorption characteristics are not ideal. The performance factors with which an in-line skater is concerned for when skating over concrete, asphalt or a composition, are speed, grip, durability and shock absorption. While all four factors are important for active sports such as hockey, grip is critical to preventing slippage and minimizing abrasion and wear.
Therefore, it is desirable to provide an in-line skate wheel which combines the resiliency and performance of a polyurethane wheel with the enhanced grip, durability and shock absorption properties associated with hollow body wheel construction and which can be casted from thermo setting polyurethane. A solution proposed in our U.S. patent application Ser. No. 08/354,374 filed Dec. 12, 1994, now U.S. Pat. No. 5,630,891, assigned to the assignee of the instant application, sets forth an in-line skate wheel with an adjustable bladder encapsulated inside the polyurethane skate wheel. Pressure in the bladder is adjustable through the use of a valve system. Such a wheel allows the skater to adjust wheel performance to match his or her needs for the particular skating maneuver to be undertaken. Since the skater has multiple performance options available without purchasing multiple wheels and without having to manually change the skate wheels, such a wheel is versatile, cost effective and convenient. While having important commercial applications, it is recognized that such an adjustable pneumatic in-line skate wheel requires the skater to manipulate the wheel each time skate conditions change and the wheel itself is relatively costly to manufacture.
Another form of in-line skate wheel with similar urethane and pneumatic benefits can be found in our U.S. patent application Ser. No. 08/595,844 filed Feb. 2, 1996 now U.S. Pat. No. 5,641,365, also assigned to the assignee of the instant application. In that application, we show a pre-pressurized pneumatic in-line skate wheel of integral construction and consisting of an annular bladder and a plurality of radially projecting bladder rods. Such an invention is relatively cost effective to manufacture but employs a relatively elaborate bladder and valve construction.
In other areas of the art, such as in the construction of variable pressure athletic shoes, it has been known to provide elastomeric bladders configured with multiple discrete chamber or open cell elastomeric foam having inlet and outlet valves. Devices of this type are shown in U.S. Pat. Nos. 4,183,156 and 4,287,250 to Rudy and U.S. Pat. No. 5,144,708 to Pekar. However, such bladders have not been generally adapted to or employed in skate wheel construction.
Thus there exists a need for an inexpensive in-line skate wheel configured with a polyurethane weight bearing tire wall securely bonded to a rigid hub and configured with a hollow annular cavity to thus minimize the volume of polyurethane required for the tire body and enhance the conformance of the tire to the underlying support surface. It is important that such a wheel be inexpensive to manufacture in a number of different tire hardness and adapted for operation on a number of different surfaces and under different operating conditions.
As can be seen, there remains a need for an in-line skate wheel which combines the benefits of the shock absorptive properties found in pneumatics with the resiliency of polyurethane, but in a manner that is easier and more cost effective to manufacture.